Known devices of the above type, such as the device described, for example, in Patent Application WO 0249918 A1, have the drawbacks of being relatively complex, expensive, and bulky, and requiring extremely precise maintenance involving considerable downtime.
Other known devices for wrapping articles comprise a wrapping wheel having a number of peripheral seats, each of which, at each operating cycle, transfers a respective group of cigarettes and a respective sheet of wrapping material from an input station to an output station along a work branch of a substantially circular path, and returns to the input station along a return branch of the substantially circular path.
Devices of this sort comprise embodiments of a first type, in which a respective heating head is associated with each seat; and embodiments of a second type, in which a number of heating heads are located in substantially fixed positions along the work branch, as described, for example, in Patent U.S. Pat. No. 4,887,408.
Both types of embodiments have drawbacks.
Embodiments of the first type comprise a relatively large number of heating heads, which are not exploited along the return branch; and the devices are relatively expensive, and relatively complicated to service : a large number of heating heads must be simultaneously functional.
In embodiments of the second type, contact between the heating heads and the sheets of wrapping material is relatively short, so that the sheets of wrapping material are not always stabilized properly about the respective groups of cigarettes.